Nonlinear Analysis of Fluid Problem with Free Surface by High-Speed Visual Processing System

本文将储油建筑物内流体的非线性晃动作为本文标题中提到的具有自由面的非线性流体问题来处理。在理论处理中，采用了基于变分原理和积分方程组的数值方法，研究了涡流现象和自由面有限振幅下常见的晃动现象。采用圆柱形和球形两种存储模型，并成功利用新引进的高速视觉处理系统，进行了振动台试验研究。对于储罐内流体的非线性响应：1)当外加激励频率在线性共振域附近时，很容易产生幅值有限的非线性晃动响应，从而使储罐壁面动压的非线性效应变得很大，在储液库的结构设计中不容忽视。2)旋转现象可描述为晃动响应的动力分量与与外激励垂直的方向上的非线性分叉现象。对于数字视觉处理系统：1)从高速视频系统获得的视觉数据可以由本图像处理单元生动地数字化，从而不需要具有超高分辨率系统的这种昂贵的系统。2)通过使用网格投影技术获得的数字化数据对于恢复变形的自由表面的原始三维数据足够精细。

Present report deals with the nonlinear sloshing of the fluid in the storage structures as the nonlinear fluid problem with free surface mentioned in the title of this report. In the theoretical treatment, numerical approaches based on both the variational principle and the integral equation are dealt with, where swirling phenomena investigated as well as usual sloshing phenomena with finite amplitude of the free surface. Experimental insurance by using the shaking table test are carried out, where the cylindrical and the spherical storage model are used and newly introduced High-Speed Visual Processing System has been successfully utilized.Results obtained by the theoretical and experimental research mentioned above can be summarized as follows. For the nonlinear responses of the fluid in the storages:1) the nonlinear sloshing responses with finite amplitude can be easily caused by the external excitation with the frequency in the neighborhood of the linear resonance domain and, as the results, the nonlinear effect of the dynamic pressure on the wall of the storage becomes so large that one can not ignore in the structural design of the liquid storage.2) swirling phenomenon can be described as the nonlinear bifurcational phenomenon between the dynamic component of the sloshing response and that in the durection perpendicular to one of the external excitation. For the digital visual processing system:1) visual data obtained from the high-speed video system can be vividly digitized by the present image processing unit that such an expensive system with super-high resolution system is not required for the present objective.2) digitized data obtained by using the grid-projection technique are sufficiently fine for restoration of the original three dimensional data for the deformed free surface.